Cleanup glade files

In preparation for switching to gtk3 cleanup the glade files. Mostly just fixing
up the widget packaging.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Open up buffer as blocking by default

In oneshot mode we want to open the buffer in blocking mode

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
sample_iio_data_continuous(): Dont treat EAGAIN as an error

EAGAIN means there is no data yet, so continue trying.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Do not insert newline after the last marker

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>